During the past two decades, Pseudomonas aeruginosa has been recognized as a pathogen which causes between 10% and 20% of infections in most hospitals. Pseudomonas infection is especially prevalent among patients with burn wounds, cystic fibrosis, acute leukemia, organ transplants, and intravenous-drug addiction. P. aeruginosa is a common nosocomial contaminant, and epidemics have been traced to many items in the hospital environment. Patients who are hospitalized for extended periods are frequently affected by this organism and are at increased risk of developing infection. The most serious infections include malignant-external otitis, endophthalmitis, endoconditis, meningitis, pneumonia, and septicemia. The likelihood of recovery from Pseudomonas infection is related to the severity of the patient's underlying disease process. The reported mortality for P. aeruginosa pneumonia is as high as 50-80%. Even with the development of newer antibiotics, resistance remains a problem necessitating combined antibiotic treatment for severe P. aeruginosa infections.
Various therapies for the management of severe P. aeruginosa infections have been evaluated for many years, with particular attention focused on virulence factors. As with most bacterial pathogens, virulence of P. aeruginosa is multifactorial and is the product of many interacting variables, involving both the bacterium and the host. Evidence suggests that the initial event in infection is the adherence of microorganisms to epithelial cells of mucosal surfaces (Bleachy). Organisms that are unable to adhere to mucosal surfaces fail to colonize because they are removed by the secretions that bathe the mucosal surfaces (Bleachy). The adherence process is dependent upon the specific recognition between bacteria and epithelial cells.
For a number of gram-negative bacteria, including P. aeruginosa, attention has been directed to surface appendages as mediations of adherence. The surface of many gram-negative bacteria, e.g., Escherichia coli, P. aeruginosa, Moraxella bovis, Neisseria gonorrhea, are covered with filamentous structures called pili or fimbriae. Pili are composed primarily of protein (pilin) and have been found to act as antigenic determinants when injected into test animals. In P. aeruginosa, strain-specific pili, such as those designated PAO, PAK, and CD4, mediate the colonization of the bacteria in humans (Doig,88).
Some P. aeruginosa bacteria lacking these pili, either through mutation or loss of the plasmid carrying the pilus gene, are incapable of colonizing mucosa. Apparently, the pili on the surface of the bacterium adhere to the lining of the throat and trachea through specific interactions with epithelial cell receptors. P. aeruginosa can utilize both pili and alginate (the principle component of the P. aeruginosa capsule) as adhesins to mediate attachment to human respiratory epithelial cells (Doig).
Equilibrium analysis of P. aeruginosa binding to human respiratory epithelial cells indicates that the Pseudomonas pilus adhesin has a considerably higher apparent affinity or binding constant than does the alginate adhesin (McEachran, 1985, 1986). These observations suggest that the pilus adhesin is likely the dominant Pseudomonas adhesin in the initiation of an infection (Irvin). Adhesion-mediated anchorage is a prerequisite for the induction of disease by P. aeruginosa.
The earlier filed co-pending patent application discloses a P. aeruginosa peptide derived from the C-terminal region of the P. aeruginosa pilin protein, and specifically, the C-terminal region which includes two Cys residues and the intervening amino acid residues. The derived region of representative peptides vary in length between 14 and 19 amino acid residues, including the two Cys residues, and are prepared in both oxidized (disulfide-linked) and reduced (non-cyclized) form. The peptides (in both reduced and oxidized form) were shown to have the following properties:
(a) ability to bind to human tracheal epithelial cells (TECs) and human buccal epithelial cells (BECs);
(b) ability to inhibit binding of Pseudomonas pilin peptide to tracheal epithelial cells (TECs) and buccal epithelial cells (BECs);
(c) ability to elicit serum antibodies which are immunoreactive with Pseudomonas pilin peptide; and
(d) ability to elicit serum antibodies which block binding to Pseudomonas pilin peptide to BECs.
It has now been discovered that the Pseudomonas-derived peptide is able to inhibit binding of unrelated bacterial and fungal organisms to human TECs and/or BECs. Thus, the epithelial cell receptor site(s) which bind the Pseudomonas-derived peptide, and thereby inhibit binding of Pseudomonas pilin (and Pseudomonas bacteria) to TECs and BECs is also involved in binding of other bacterial and fungal organisms to these target cells. It has further been shown, in studies conducted in support of the present invention, that monoclonal antibodies prepared against the Pseudomonas-derived peptide are effective in blocking fungal cell adherence to BECs.
These combined findings show that the Pseudomonas-derived peptide, and antibodies produced in response to the peptides, are capable of inhibiting bacterial and fungal infections in which the infecting microorganism has surface proteins which are antigenically crossreactive with antibodies produced against the C-terminal, disulfide-linked peptide region of P. aeruginosa pilin protein.